IgG4-Related Disease — Clinical Case

DCE Long Case

Patient brief (provided to trainee)

Patient: Mr Robert Chen, 62 years old, retired chemical engineer. [1]

Presenting complaint: Six weeks of painless jaundice with dark urine and pale stools. Three months of gradual, painless enlargement of both submandibular glands. Four weeks of intermittent bilateral flank discomfort. A 4 kg unintentional weight loss over three months, attributed by the patient to loss of appetite from the jaundice. [1]

Past history: Mild asthma and allergic rhinitis (on a salbutamol inhaler and an intranasal steroid spray). Hypertension (on ramipril 5 mg daily). No prior surgery. No diabetes. No allergies. Never smoked. Drinks 6 standard drinks a week. [1]

Examination findings (trainee elicits): Deeply jaundiced sclerae and skin, with excoriation marks from pruritus. Firm, non-tender, bilateral submandibular gland enlargement (each 3 cm), with mild enlargement of the lacrimal glands. No cervical, supraclavicular or axillary lymphadenopathy. Cardiovascular and respiratory examination unremarkable (blood pressure 142 over 88). Abdomen soft, non-tender; no palpable gallbladder, no organomegaly. No peripheral oedema. [1]

Investigations: Bilirubin 110 micromol per litre, ALP 460 U per litre, ALT 120 U per litre, albumin 34 g per litre, creatinine 150 micromol per litre (baseline 90), eGFR 42. Full blood count normal, eosinophils mildly elevated at 0.6 billion per litre. IgG4 3.2 g per litre (normal less than 1.35), total IgG 21 g per litre. CA19-9 28 U per mL (normal less than 37). Anti-Ro and anti-La negative, ANA weakly positive at 1:80. Complement C3 mildly low. Hepatitis B and C negative, IGRA negative. [1]

Imaging: Contrast CT — a diffusely enlarged, capsule-rimmed pancreas with delayed enhancement and a narrow pancreatic duct, no focal mass, no vascular encasement; a mid common bile duct stricture; bilateral wedge-shaped low-attenuation renal cortical lesions; a small periaortic rind encasing the lower aorta and proximal iliac vessels. MRCP confirms the biliary stricture and a nondilated intrahepatic tree. FDG-PET-CT — avid uptake in the pancreas, the submandibular and lacrimal glands, the renal lesions and the periaortic rind. [1]

Candidate's opening statement (SASPOP format)

"Mr Robert Chen is a 62-year-old retired chemical engineer presenting with six weeks of painless obstructive jaundice, three months of progressive painless enlargement of both submandibular glands, and four weeks of flank discomfort with a rising creatinine. He has mild asthma and allergic rhinitis and hypertension. His main problems are: [1]

1. IgG4-related disease with multi-organ involvement — type 1 autoimmune pancreatitis, IgG4-related sclerosing cholangitis, Mikulicz syndrome, IgG4-related kidney disease and early retroperitoneal fibrosis — in the active inflammatory phase, supported by the avid FDG uptake and the marked IgG4 elevation.
2. Obstructive jaundice from the pancreatic and biliary involvement.
3. Renal impairment from bilateral ureteric obstruction by the periaortic rind — the urgent, potentially reversible problem.
4. The exclusion of pancreatobiliary malignancy, which the pattern and the normal CA19-9 favour against but which tissue must confirm.
5. The treatment-related risks of glucocorticoids and rituximab in a 62-year-old with hypertension.
6. The psychosocial impact of a new multisystem diagnosis on a man in retirement." [1]

Structured problem list and integrated management plan

Problem 1 — Multi-organ IgG4-related disease (active inflammatory phase). Confirm the clinicopathological diagnosis with endoscopic ultrasound-guided core biopsy of the pancreas (sufficient tissue for histology, IgG4 immunostaining and flow cytometry), and apply the 2019 ACR and EULAR classification criteria (entry criterion met, no exclusion criterion, inclusion score well above 20). Treat with prednisolone 35 mg daily for two to four weeks then taper, with bone protection and pneumocystis prophylaxis, and plan a rituximab course as the steroid-sparing maintenance, having screened for hepatitis B and tuberculosis [1][2][3][4].

Problem 2 — Obstructive jaundice from type 1 AIP and IgG4-related sclerosing cholangitis. Place a biliary stent at ERCP if the cholestasis or the cholangitis risk demands it; otherwise the steroid response usually resolves the jaundice within two weeks. Monitor the liver function and reimage the biliary tree. Distinguish from primary sclerosing cholangitis (no IBD, marked IgG4, dramatic steroid response) and from cholangiocarcinoma (tissue) [1].

Problem 3 — Renal impairment from bilateral ureteric obstruction (retroperitoneal fibrosis). This is the priority. Decompress with bilateral ureteric stents or nephrostomy today, because the renal recovery depends on the duration of obstruction; then treat the active inflammation with prednisolone. Exclude secondary causes of retroperitoneal fibrosis (malignancy, drugs, radiation) — the biopsy and the drug history do this [1][3].

Problem 4 — Exclusion of pancreatobiliary malignancy. The pattern favours IgG4-related disease (diffuse sausage-shaped pancreas, no vascular encasement, normal CA19-9, marked IgG4, multi-organ involvement), but cancer can elevate IgG4 mildly and coexist. Obtain adequate tissue before immunosuppression. Do not rely on a steroid response to make the diagnosis, because lymphoma and even cancer can shrink transiently on steroids [1][3].

Problem 5 — Treatment-related risks. Bone protection (calcium, vitamin D, a bisphosphonate or denosumab where indicated by fracture risk) with the steroid course; pneumocystis prophylaxis with co-trimoxazole; blood pressure and glucose monitoring; hepatitis B and tuberculosis screening, and vaccination updating, before rituximab; monitoring of immunoglobulins and B-cell counts with repeat rituximab [3][4].

Problem 6 — Psychosocial impact. Frame the diagnosis as treatable but relapsing; address the "is it cancer?" fear directly; explain the steroid burden and the rationale for rituximab; coordinate rheumatology, gastroenterology, nephrology and ophthalmology with a named lead clinician; and set up a structured surveillance plan covering renal and hepatic function, serum IgG4 trends, B-cell counts and periodic imaging [3].

Probing questions and model answers

Examiner: Why are you confident this is not pancreatic cancer? [1]

"The pattern is strongly in favour of type 1 autoimmune pancreatitis: the diffusely enlarged, capsule-rimmed, sausage-shaped pancreas rather than a focal mass; the absence of vascular encasement; the normal CA19-9; the IgG4 more than twice the upper limit; and the multi-organ involvement with the submandibular glands, the renal lesions and the periaortic rind. Against this, cancer can elevate IgG4 in 10 to 15 per cent of cases, and a focal cancer can coexist with an unrelated IgG4 elevation. I will obtain adequate tissue before immunosuppression, and I will not rely on a steroid response to confirm the diagnosis." [1][3]

Examiner: How would you interpret a normal serum IgG4 in this patient? [1]

"A normal IgG4 would not change my diagnostic reasoning, because 20 to 30 per cent of biopsy-proven type 1 autoimmune pancreatitis are seronegative. The diagnosis is clinicopathological, with histopathology as the gold standard. The IgG4 is supportive when elevated but never exclusionary when normal." [1]

Examiner: What histopathology do you expect, and what are its limits? [1]

"The triad of a dense lymphoplasmacytic infiltrate rich in IgG4-positive plasma cells, storiform fibrosis and obliterative phlebitis, with an IgG4 to IgG ratio above 40 per cent. The IgG4 cell count threshold is organ-specific (above 30 per high-power field for pancreas), and the count is not diagnostic in isolation — I read it with the triad, the imaging and the clinical context, and I use flow cytometry to exclude lymphoma." [1][2]

Examiner: Why rituximab rather than continued steroids? [1]

"Because this is multi-organ disease and the relapse rate during a steroid taper is 40 to 50 per cent. Continued steroids compound the cumulative toxicity (osteoporosis, diabetes, infection) without controlling the relapsing course. Rituximab depletes the B-cell compartment that drives the T-cell-mediated inflammation, is highly effective, and is now used as a planned maintenance strategy rather than only as rescue. I screen hepatitis B and tuberculosis first, update vaccinations before the first dose, and monitor the B-cell count and immunoglobulins." [3][4]

Examiner: How do you handle the fibrotic component? [1]

"The ureteric obstruction has a mechanical component that I relieve with stents regardless of the inflammatory activity, and a mature periaortic rind will not respond to escalating immunosuppression. I treat the complications mechanically and reserve the immunosuppression for the metabolically active, FDG-avid lesions. Escalating steroids for a burnt-out fibrotic lesion adds toxicity without benefit." [1][3]

Key insight for the candidate

"The single most important lesson in this case is that IgG4-related disease is a unifying multisystem diagnosis, but it mimics cancer and cancer mimics it. The candidate who treats the elevated IgG4 as diagnostic, or who starts a steroid trial without adequate tissue, has missed the central reasoning task. The correct approach is to recognise the multi-organ pattern, confirm the diagnosis with the histopathology triad and the classification criteria, protect the threatened organ (the obstructed kidney) mechanically, exclude cancer with tissue, and then treat the inflammation with steroids and plan rituximab for the relapsing course. The serum IgG4 is a biomarker, not a verdict — elevated or normal, it never stands alone." [1][2][3]